Among commonly used radiation detectors, semiconductor detectors have the advantage of good energy resolution compared with scintillator detectors. And semiconductor detectors of small size can be very fast. This is because that the time required to collect the carriers over a typical length of 1 mm can be less than 10 ns for a typical semiconductor like silicon. However, for detecting low energy particles, this fast timing is usually not achievable if we need reasonable energy resolution at the same time. This is because the signal generated by the low energy (less than a few hundred keV) particles is small (the signal is proportional to the energy of the particles) and signal to noise ratio is low. If we want fast timing, we will need to increase the bandwidth of the preamplifier, which will in turn increase the series noise of the preamplifier. And for fast detection, the series noise of preamplifier dominates the noise. With large noise, the energy resolution worsens.
Accordingly, there is a need for a signal amplifier that overcomes the shortcomings stated above.